This invention relates generally to the field of mailing machines, and more particularly to a component of a mailing machine that moistens flaps of envelopes to be sealed by the mailing machine.
Generally, a mailpiece transport on a mailing machine transports envelopes and other mailpieces along a feed path so that various functions may be performed on the mailpiece at different locations along the feed path. For example, at one location along the feed path the mailpiece may be weighed, at another location the mailpiece may be sealed, and at a further location an indicia for postage may be applied to the mailpiece. Drive rollers and/or drive belts may be employed to contact the mailpiece to propel the mailpiece along the feed path.
The step of sealing a mailpiece may be considered to include three sub-steps: (a) “stripping” the envelope flap (i.e., opening the flap so that moisture can be applied to the flap), (b) moistening the gummed portion of the flap, and (c) closing the flap and applying pressure to the envelope and flap so that the moistened gummed portion of the flap adheres to the body of the envelope. Known mailing machines include a sealing module that includes devices or sub-modules for performing each of these sub-steps.
Envelope flap moistening sub-modules have been found to exhibit certain problems. Some flap moisteners employ a brush or piece of felt that is moistened by a wick that draws fluid to the brush or felt from a reservoir. It can be problematic with such moisteners to assure that the brush or felt is wetted to a suitable degree. Too much wetting of the brush or felt may cause too much moisture to be deposited on the envelope, which may adversely affect printing on the envelope, alter the appearance of the envelope, or damage the contents of the envelope. Too little wetting of the brush or felt may cause the gummed portion of the envelope flap to be insufficiently moistened, resulting in unreliable sealing. Maintaining a constant degree of wetting of the brush or felt over time also presents difficulties; for example, the amount of fluid transferred to the brush or felt from the wick may vary with the amount of fluid in the reservoir. While moistening a sequence of envelope flaps, or even during the course of moistening a single flap, the brush or felt may dry out to such an extent that inadequate moistening of a flap or a portion of a flap occurs.
There may also be an issue concerning adhesive transfer from the envelope flaps to the brush or felt, possibly leading to build-up of adhesive on the brush or flap, and a need to frequently clean or replace the brush or felt.
In another type of flap moistener, a movable spray nozzle is provided to spray moistening fluid on the gummed portion of the flap. Sensors are provided to detect the edge of the flap, and the spray nozzle is moved to follow the gummed portion of the flap based on output from the sensors. Moistening fluid is continuously dispensed from the nozzle.
Because of inherent delays in moving the spray nozzle, the sensors may need to be placed considerably upstream in the envelope feed path, thereby leading to a relatively large footprint for the moistening device. In addition, the envelope may shift transversely over the relatively long distance from the sensors to the nozzle, so that the gummed portion of the flap may not be accurately tracked by the nozzle.
Furthermore, delay in moving the nozzle may cause leading and trailing portions of the gummed portion of the flap to be missed by the spray. This may result in unreliable sealing. It may also be difficult for the nozzle to be moved to follow certain flap profiles, such as rectangular or pointed flap profiles. This too may result in unreliable sealing. Changes in direction by the nozzle may cause fluctuation in pressure in the moistening fluid, preventing the stream of fluid from being reliably directed to the gummed portion of the label. Again unreliable sealing may result.
The requirement that the nozzle sometimes be accelerated quickly to follow the flap contour may make significant demands on the power supply for the motor that moves the nozzle. The motor may also be a source of noise that may disturb the operator of the mailing machine. Also, the continuous flow of moistening fluid must be collected and recirculated, causing the flap moistener to be rather complex in its construction. In addition, recirculated fluid may be contaminated with paper dust and/or adhesive from the envelope flap, which may lead to clogging of nozzles, pump, tubing and/or filters.
Another disadvantage of the continuously flowing fluid is that if the mailing machine happens to stop with an envelope at the moistening station, a very excessive amount of moisture may be directed to the envelope.
U.S. Pat. No. 3,911,862 discloses an envelope flap moistening apparatus in which one movable or two or more stationary nozzles are operated responsively to envelope sensors to spray strips of moistening fluid on the gummed portion of the envelope flap. Specifically, the '862 patent requires the envelope flap to be opened no less than 90° from the envelope body such that the envelope flap is perpendicular to the envelope body. Nozzles located adjacent to the envelope body then spray moistening fluid onto the gummed portion of the envelope flap. There are several disadvantages with this type of arrangement. First, the amount of space needed to accommodate the moistening apparatus, including the nozzles, is large, since the nozzles must be situated adjacent to the envelope body. Another disadvantage is the length of the envelope feed path necessary to perform the moistening and sealing functions. There must be a sufficient distance between the envelope flap opening device, typically referred to as a stripper blade, and the nozzle location to ensure that the envelop flap has been opened to the required right angle with the envelope body. If the envelope flap is not at a right angle to the envelope body, the moistening fluid will not be sprayed on the gummed portion. If the moistening fluid is not sprayed on the gummed portion, the envelope may not properly seal. There also needs to be a sufficient distance between the nozzles and a sealing nip to allow the envelope flap to move from the open position, i.e., a perpendicular position with respect to the envelope body, to a closed position before passing through the sealing nip. If the distance between the nozzles and the sealing nip is insufficient, buckling of the envelope flap can occur, thereby resulting in improper sealing of the envelope, or jamming of the envelope along the transport mechanism. Either of these results can cause dissatisfaction with the moistening apparatus. Thus, to ensure proper moistening and sealing, the device in the '862 patent requires a significant amount of distance from end to end, thereby increasing the overall length of a mailing machine in which the apparatus is installed. There exists a need, therefore, for a moistening apparatus that is more compact and has a minimal end-to-end distance, thereby fitting more conveniently within a mailing machine than the apparatus disclosed in the '862 patent, while still ensuring proper moistening and sealing of envelopes.